Control slide valve



United States Patent [56} References Cited UNITED STATES PATENTS 2,715,913 8/1955 Taylor 137/625.25

2,916,051 12/1959 Taylor 137/625.64 3,122,616 2/1964 Rice etal ..137/625.46XR 3,338,268 8/1967 Houser et al l37/625.66

FOREIGN PATENTS 1,150,454 8/1957 France 137/625.63

718,793 11/1954 Great Britain 137/625.66

Primary Examiner Henry T. Klinksiek Attorney-Beaman and Beaman AlBSTlRAQT: A slide valve spool slidable arranged on a slide valve face plate provided with connections for different pressure stages of a working gas serves to control the gas flow from one connection to the other. The spool member consists ofa material with high thermal conductivity and has covered its recess in contact with the gas flow and its sliding face with a plastics coating of good sliding ability. With this valve spool icing can be avoided and lubrication is necessary only after long periods oftime.

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Fig. 1

HH'l/ "X\ I! I. 1 W: 2 55 HI]! i W4 H 7 1' W 59 1| I 54 1 1. HU i 55 I 2 HI! 86 8I I 61 i L M3 2x1 20 19 Z 85 189 H H0 A 1 I I M my 74 57 H114 M l I WPJZA .7 1 1 Ill I i" M: 3m 15 13 22 u 83 85 W 2 I k/ 3 57+ 57' ii 2 T 4,159 FA g /g [L7 ZZZ; IT I! i I WZZ 2 i A Fl- [I Ld/;4 I l 52 F7722 33 1 I; I B7 i i f 43 $11 "9- 3 W2 1f 47 US. PATENT 3,522,823 CONTROL SLIDE VALVE CROSS-REFERENCE TO A RELATED APPLICATION The United States Patent Application Ser.No. 546,735 of the applicant filed on May 2, 1966, now patent 3,405,606, describes a control device for a double acting pressure medium energized servo-motor. That servo-motor and control device comprises essentially in combination a cylinder with a piston adapted to reciprocate therein and separating the cylinder into a first and a second working chamber, a source of said pressure medium and a low pressure reservoir into which said pressure medium can flow off, a control valve member being reciprocable in a control valve member housing adapted to rule a first, a second and a third control chamber, a first and a second expansion valve arranged at the opposite sides of said first and second working chamber, respectively, and normally resiliently forced into the closed position thereof, said valves being adapted to be opened by said piston near the reversal points thereof, means for connecting the sides of said first and said'second expansion valve oppositeto said working chambers both to said reservoir and said first and said second control chamber, respectively, check valve means between said third control chamber and said first and said second control chamber, respectively, means for communicating said third control chamber with said source of pressure medium, said low pressure reservoir and with said first and said second working chambers and a slide valve member operatively connected to said control valve member for governing the communication between said reservoir and said first and second working chambers, respectively.

The present invention generally relates to a new slide valve spool for controlling thegas flow from a connection of higher pressure to a connection of lower pressure. The new slide valve spool is particularly suited for control devices described in said prior application.

BACKGROUND OF THE INVENTION The field of the invention is the control of a servo-motor which actuates the working piston of a machine, i.e. a pump. The control mechanism for the reversal of servomotors actu ated with pressurized air like that described in applicant's prior application tends to become icy as is the case with many compressed-air operated apparatuses, particularly near an expansion region of the compressed-air. Especially the slide valve spool of the control mechanism underlies the icing because the pressure drop of the compressed air when overflowing through said slide valve spool into the low pressure reservoir causes cooling and finally icing of the spool and the adjacent parts of the control mechanism.

It is an object of the invention to provide a slide valve spool for controlling the air flow from several connections of higher pressure to a low pressure reservoir without the danger to become icy. Another object of the invention is to provide a slide valve spool with good sliding ability so that servicing and lubrication of the spool is unnecessary for long periods of time.

SUMMARY OF THE INVENTION According to the present invention the slide valve spool member consists of a material with good thermal conductivity and has inserted in its recess in contact with the gas flow an inlay of plastics with a good sliding ability, the sliding surface ofthe spool being covered also with said plastics. The material of said slide spool has preferably a thermal conductivity in the range from 0,3 to 0,7 cal. cm". sec". grd' and a useful material is aluminum. The inlay is preferably made by injection molding of thermoplastics, such as polyethylene.

The danger of icing of the slide valve spool as well as of the slide main face plate is eliminated on one hand by the very smooth sliding -coating which requires no lubrication and on theother hand by the good heat transfer from the relatively warm compressed-air flowing through the control mechanism and entering the slide valve spool to the spool member and from there to the spool inlay which underlies the cooling by the expanding air.

A remarkable technical progress finally resides in the fact that with eventual wear only the spool inlay must be replaced rather than the whole slide valve spool as hitherto was customary in order to assure functioning of the control mechanism and the servo-motor and the working machine connected thereto.

Further features and advantages of the invention appear in the following detailed description of a preferred embodiment of the invention taken together with the drawing. The drawing and detailed example are provided by way of illustration and not of limitation.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 shows a longitudinal sectional view of a double acting single-cylinder pump including a control valve together with a slide valve spool according to the present invention.

FIG. 2 shows in an enlarged scale a partially sectional side view ofa control valve member connected with the slide valve spool according to the present invention.

FIG. 3 shows a sectional view of the slide valve spool, the control valve member and the slide face plate, taken along the line Ill-Ill ofFIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The double-acting single-cylinder servo-motor or pump consists of a special suitably designed working cylinder 33, a known per se power cylinder 11 and a control housing 51 with the control device arranged therein.

The power cylinder 11 is respectively covered at its upper and lower ends by cylinder covers 12 and I3. In order to effect a sealing, annular O-rings I4 are provided; the covers are fastened to the cylinder by means of screws IS. A power piston I7 is sealed by means of an O-ring I8 in the power cylinder.

Piston I7 is connected with a piston rod 25 by means of a screw 19 in the form of a countersunk or hexagon screw. Here, an annular O-ring 20 effects the sealing of the upper and lower cylinder chambers with respect to each other.

FIG. I shows that piston rod 25 has its lower end designed in the manner ofa working piston with a builtin check valve. Sealing of the working piston is effected by sealing rings 43 between which the sealing bushing 44 is situated. A piston rod nut 45 retains the sealing on its outer diameter, while the inner diameter is forming the seat for a valve ball 41. In the lower cover I3 of the power cylinder 11, a sealing ring 22 is disposed below a holding disc 21. This holding disc has fastened thereto by means of screws I an intermediate flange 2. A sealing prevents leakages at the bores for the screws 1. In the inter mediate flange 2, a pressure sleeve 3 is seated which supplies the necessary bias on upper and lower sealing rings 5 and 7 via a pressure disc 4 and an intermediate ring 6. The lower sealing ring 7 abuts a bottom ring 8. The working cylinder 33 is provided with a thread at its upper end which is screwed into the lower portion of the intermediate flange 2. At its lower portion, the working cylinder carries a suction valve 48. Sealings 46 are inserted in the intermediate flange and the suction valve. The valve body of the suction valve forms a valve ball 40 which, in its one end position is abutting a cap 49. This cap 49 is retained by means of a circlip 47. The piston rod 25 is visible through a transverse bore S in the intermediate flange. When the sealing rings 5 and 7 are failing, this opening will prevent the intrusion of the material to be conveyed into the power cylinder.

As is shown in FIG. I, the control valve housing SI is fitted in the upper and lower cylinder covers by means of studs 53, short studs 54 and cap nuts 55. Washers 56 are placed between the control housing and the cap nuts. The fluid passages extending within the control valve housing and the cylinder covers are sealed at the point of contact between the housing and the covers by means of flange seals 57. Two control valve housing covers 70 have their journals projecting into the longitudinal through bore in the control valve housing 51 and are sealed by means of O-rings 59. The control valve housing covers 70 are retained by countersunk screws not shown in the drawing. The control piston which is axially movable within the control housing is formed mirror-symmet rically with respect to the center plane.

The control valves and the control passages as well as the main passages of the fluid are likewise arranged mirror-symmetrically with respect to the center plane of the power piston extending vertically to the axis of the stroke. The control valve piston 61 is arranged displaceably within the longitudinal bore of the control valve housing 51 between the journals of the control valve housing covers. It is sealed in the longitudinal bore by means of O-rings 74. In the control valve piston 61, each threaded plug 71 is inserted from above and from below. These threaded plugs 71 are retaining two O-rings which are forming valve seats for a ball 66 movable between them as a valve member. The valve seating rings 64 are kept at a certain space from one another by a spacer sleeve 65. The control valve housing covers 70 have inserted therein thin braking studs 73 lifting the valve ball 66 from the sealing rings forming the valve seats at the end of the reversing movement of the control piston 61 (FIG. 2 and 3). The control piston 61 is provided with a contraction 62 at its outer periphery with a slide valve spool 67 fitted therein. The valve spool surface engaging the contraction 62 has a semi-circular section. According to the present invention the slide valve spool 67 has inserted in its recess facing away from said semi-circular engagement surface an inlay 68 of plastics. This inlay covers the spool recess as well as the sliding surface of the spool. The material of the slide valve spool 67 is aluminum and the material of the inlay coating is a thermoplastic which produces a coating with a very smooth surface.

The control valve housing 51 is provided with a laterally disposed center opening which is covered by a slide valve face plate 69. The slide valve face plate 69 is provided with three bores for the fluid. Of the three channels in this plate the upper and lower channels HU and H are alternately bored and are closed by plugs 72. The third bore LA serves to discharge the fluid to its low pressure reservoir. The slide valve face plate is screwed to the control valve housing 51. A sealing layer 75 is disposed between these two members. instead of the double-acting check valve in the control valve piston 61, under certain circumstances, also two single-acting check valves may be employed.

The threaded insert 81 ofthe relief valve 80 has its threaded end threaded into corresponding bores in the cylinder covers 12 and 13. The sealing rings 85 seal the inner space of the valve housing against the atmosphere and the cylinder inner space. The valve pin or body 82 functioning as a valve member has its collar pressed against a sealing ring 89 by means of a valve spring 83, with the sealing ring 89 abutting a circlip 87 via a disc 86. Towards the other side, the valve spring 83 is effective on another sealing ring 89a via a disc 88, said further sealing ring 89a being retained via another disc 88 by a second circlip 90. The sealing rings 89 and 89a are dimensioned such that they have a sealing effect on both their outer and inner periphery. With the valve closed the sealing ring 89 seals in addition the transverse bores 82a in the valve pin 82 by lying close to the collar surface of said pin because said transverse bores 82a are smaller in diameter than the width of the O-ring 89. The transverse bores in the valve body 82 are constantly communicating with the atmosphere through the longitudinal bore in said valve body 82. With the relief valve 80 closed, i.e. with the collar face of the valve body 82 abutting the O-ring 89, the interior of the relief valve is thus sealed against the atmosphere. in the open position, as shown, the interior space of the valve is thus in communication with the atmosphere. ln both cases, the inner space ofthe cylinder is not communicating with atmosphere nor with the interior of the relief valve that means neither with the valve closed nor with the valve in its open position.

Now, the mode of operation of the control of the power cylinder in accordance with FIG. 1 will be described. ln the working condition as shown in FIG. I, the reversal of the piston 17 has just been effected. At this moment, the piston starts its upward movement in the power cylinder, and the compressed air flows into the control housing. Compressed air arrives at the flange surface of the lower cylinder cover 13 through the main passage HU which is disposed in the top portion of the slide valve face plate 69 which is at this moment exposed by the slide valve spool 67, and along a passage (not shown) through an angular bore in the control valve housing 51, the compressed air arrives at the lower cylinder room through an enlarged bore for the lower stud 53. The manner in which this main passage HU extends is a mirror image of the main passage HO shown in the drawing. The piston moves upwardly under the pressure of compressed air entering between the cylinder cover 13 and the power piston 17. The air present in the space between the upper cylinder cover and the power piston flows through the upper main channel HO. This passage extends as an enlarged bore for the studs 53 in the upper cylinder cover 12 into the control valve housing 51 and therein through the angular bore to the slide valve face plate 69. The angular bore is closed towards the upper side by the plug 52 fastened in the control housing. The air arriving in the main passage H0 is reversed in the slide valve spool 67 and leaves the valve face plate by the air exit LA. During the entire upward movement of the power piston, the pressure of the compressed air is prevailing in the inner space of the control valve. In the position shown, the compressed air could flow through the transverse bore in the control piston 61 and the spacer sleeve 65, the upper valve seating ring 64, the longitudinal bore in the upper threaded plug 7] and the angular bore in the journal of the upper control housing cover through the upper flange surface comprising the upper control passages StO and to the interior of the control valve through said control passage. Only if the power piston 17 is abutting against the relief valve member 82 and moves it against the effect of the spring 83, will the upper control passage be connected with the atmosphere. With this, the pressure above the valve member 66 in the control housing and the bores will drop, and the ball valve member 66 will be pressed against the upper valve seat by the compressed air present below the ball. By this, the passage for the compressed air through the upper O-ring 64 will be blocked. Accordingly, atmospheric pressure will now prevail on the upper side ofthe control piston 61 with the pressure of the compressed air prevailing on the underside and, therefore, the control piston will be driven upwardly and will in so doing take along with it the slide disposed in the contraction of the piston along the slide valve face plate. in order to attenuate the impact of the control piston 61 against the control housing cover 70, the pins 73 lift the valve body 66 from the valve seat shortly before the impact occurs. in this manner, the subsequent reversing operation is facilitated at the same time because, at this moment, the valve member 66 of the check valve is freely floating between the valve seating rings 64. The control valve now exposes the main passage HO and connects the main passage HU with the air outlet LA. lmmediately on completion of the reversal operation, the compressed air may flow through the lower O-ring 64 and the lower control passage StU to the lower control valve. With this, the lower valve is prepared for the next reversal. During the downward movement of the piston the roles of the mirrorsymmetrically arranged valves and parts in the control housing are exactly exchanged. The effect of the working piston obtained during the movement of the power piston and thus the effect of the delivery member is as follows:

During the upward stroke of the working piston, the ball valve in the working piston is closed, the suction valve is open. During this stroke, the amount of the material to be delivered which corresponds to the differential diameter between the working piston and the piston rod is expelled at FA. At the same time, the amount corresponding to the diameter of the working piston is drawn in at FE. During the downward stroke, the suction valve closes, and the ball valve in the workin'g'piston opens and an amount of material to be delivered in correspondence with the differential diameter between working piston and piston rod is again delivered.

The construction of the slide valve spool 67, 68 according to the invention is independent from the drive of the control mechanism, that means is equally advantageous when using a control mechanism without a linkage or driven by a linkage.

I claim:

l. A slide valve for controlling the flow of a pressurized gas particularly suitable to prevent valve icing, comprising, in combination, a passage plate having a smooth face surface, a plurality of gas passages defined in said plate intersecting said face surface, a slide valve movably mounted adjacent said plate formed of a metallic material having high thermal conductive characteristics, a face defined on said slide valve disposed toward said plate face surface, a recess defined in said slide valve face selectively communicating with said passages whereby said recess serves to selectively establish communication between said passages, and a synthetic plastic bearing member of a material having self lubricating characteristics interposed between said slide valve and said plate face surface, said bearing member being of a thin wall configuration and including a recessed portion corresponding in configuration to said slide valve recess and received therein and a flat portion disposed about said recessed portion interposed between said plate face surface and said slide valve face wherein said slide valve does not directly engage said passage plate and said bearing member moves with said slide valve.

2. In a slide valve as in Claim 1 wherein said bearing member flat portion is of the configuration corresponding to the shape of said slide valve face whereby said entire slide valve face is covered by said bearing member.

3. A slide valve as in Claim 1 wherein said slide valve is formed ofaluminum. 

